1. Field of the Invention
The present invention relates to an IC card which enables its memory capacity to be checked, and a memory IC which is mounted on such an IC card.
2. Description of the Related Art
FIG. 4 shows the structure of a conventional IC card. A decoder 2 is connected to a connector 1 via a memory selection signal line 5 and a card enable signal line 6. The decoder 2 is also connected to a memory IC 3 for storing data via a chip enable signal line 7 and to a memory IC 4 for storing the capacity of the IC card via a chip enable signal line 8. Both the memory IC 3 for storing data and the capacity storing memory IC 4 are connected to the connector 1 via an address 9, a read-out control line 10, a write control line 11 and a data line 12. Data, such as the memory capacity of the IC card, is stored beforehand in the capacity storing memory IC 4.
When the IC card receives a card enable signal CE having a low level via the card enable signal line 6, it enters the operation enabled state, and the decoder 2 thereby outputs a chip enable signal selectively to either of the memory IC 3 for storing data and the capacity storing memory IC 4. Selection between the memory ICs 3 and 4 is made according to the level of a memory selection signal MS input via the memory selection signal line 5. For example, when memory selection signal MS is at the high level, the memory IC 3 is selected. When the memory selection signal MS is at the low level, the capacity storing memory IC 4 is selected. In both the memory ICs 3 and 4, the data stored in an address designated by the address line 9 is read out onto the data line 12 by lowering the read-out control line 10 to a low level and by raising the write control line 11 to a high level. The data on the data line 12 is written on an address designated by the address line 9 by raising the read-out control line 10 to a high level and by lowering the write control line 11 to a low level.
To check the memory capacity of the IC card, the card enable signal CE is lowered to a low level, the memory selection signal MS is lowered to a low level, the read-out control line 10 is lowered to a low level, the write control line 11 is raised to a high level and the address of the memory IC 4 for storing the memory capacity is designated by the address line 9, whereby the memory capacity is read out onto the data line 12.
Such a conventional IC card requires the memory capacity storing memory IC 4 in addition to the data storing memory IC 3, and thus has a complicated circuit structure.